When manufacturing semiconductor devices on substrates like semiconductor wafers, for example, silicon wafers, metal is deposited on the substrate, for example, on a non-processed backside of the substrate or a processed front side of the substrate or parts thereof, to provide electrical contacts to the semiconductor devices and/or to provide interconnects between various parts of the devices manufactured. Various metal deposition techniques are conventionally used, for example, sputtering, galvanization or electroless plating. One example for electroless plating is electroless nickel plating, where an autocatalytic deposition of nickel phosphorous (NiP) by immersion of the substrate into a plating bath may be used. In some cases, this may lead to the formation of nickel flitter, for example in a peripheral region of the substrate. Similar phenomena may occur using other metals. Such flitter has a poor adherence to the substrate, which constitutes a quality risk as they may detach from the peripheral region of the substrate and, e.g., reach other portions of the substrate, e.g., portions where devices are formed, and which might require additional measures when manufacturing devices, like regular change of filters or of a plating bath used or a separate process step for removing the flitter, which additional measures may increase manufacturing costs. In case of unsuccessful measures, production yield is decreased when due to flitter substrates have to be discarded.
Various embodiments of the present invention will be described in the following with reference to the accompanying figures. It is to be noted that these embodiments have illustration purposes only and are not to be construed as limiting the scope of this application in any way. Features of various embodiments described may be combined with each other unless specifically noted otherwise. On the other hand, describing an embodiment with a plurality of features is not to be construed as indicating that all those features are necessary for practicing the techniques disclosed herein or shown in the drawings, as other embodiments may comprise, for example, less features and/or alternative features.
In various embodiments discussed and described in more detail below, a substrate, for example, a semiconductor wafer, is provided with a covering layer, for example an imide layer, at a peripheral region thereof using inkjet printing techniques. The covering layer may, but need not comprise an isolation material. The covering layer may serve as a passivation layer and/or a protection layer in some embodiments. In some embodiments, the printing is restricted to the peripheral region, i.e., other regions of the substrate are not printed on. In some embodiments, this may occur prior to a metal deposition, for example, comprising electroless plating like the electroless plating of nickel. However, applications of the techniques and apparatuses described in the following are not limited to specific metals or substrates. In some embodiments, by forming the covering layer at the peripheral region of the substrate, formation of flitter like nickel flitter may be prevented, minimized or reduced.